Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$151.58	3.558%	$156.9732	$156.97	$156.95	$157.00
Purchase #2	$248.32	9.196%	$271.1555	$271.16	$271.15	$271.20
Purchase #3	$206.77	9.839%	$227.1141	$227.11	$227.10	$227.10
Purchase #4	$199.46	5.112%	$209.6564	$209.66	$209.65	$209.70
Purchase #5	$177.25	10.752%	$196.3079	$196.31	$196.30	$196.30
Purchase #6	$11.39	11.280%	$12.6748	$12.67	$12.65	$12.70
Purchase #7	$109.62	4.411%	$114.4553	$114.46	$114.45	$114.50
7 purchase totals =	$1,104.39		$1,188.3372	$1,188.34	$1,188.25	$1,188.50